Laminated ink jet recording head with plural actuator units connected at outermost ends

ABSTRACT

An actuator unit for a laminated ink jet recording head includes: a first cover member for forming a vibrating member having piezoelectric vibrators on a surface thereof; a spacer for forming pressure generating chambers with a surface thereof sealed by the first cover member; a second cover member having ink jetting outlets and ink flowing inlets, each ink jetting outlet causing the corresponding pressure generating chamber to communicate with a corresponding nozzle opening of a flow path unit at one end of the pressure generating chamber, each ink flowing inlet causing the corresponding pressure generating chamber to communicate with a common ink chamber of the flow path unit at the other end of the pressure generating chamber. The actuator unit is prepared by laminating and fixing the first cover member, the spacer and the second cover member. A pitch at which the pressure generating chambers are arranged is set to a value equal to or smaller than a pitch at which the nozzle openings are arranged; widths of partition walls on outermost ends of pressure generating chambers located on the outermost ends are set to a value equal to or greater than a width of a partition wall defining adjacent pressure generating chambers and equal to or smaller than 1/2 of the nozzle opening arrangement pitch. An increase in the distance between the adjacent pressure generating chambers at the contact line between two actuator units is set to within a range of values substantially equal to the width of the partition wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an actuator unit for a laminated ink jetrecording head and a method of fabricating such an actuator unit. Theactuator unit has piezoelectric vibration elements, expandable andcontractible pressure generating chambers, ink flowing inlets, and inkjetting outlets, and is adapted to construct a recording head whilebeing laminated on a flow path unit having common ink chambers andnozzle openings formed therein.

2. Description of the Related Art

For example, as disclosed in Unexamined Japanese Patent Publication No.Hei. 6-40035, an ink jet recording head, in which piezoelectricvibration elements are stuck to one region of a resilient plate thatconstitute pressure generating chambers and in which ink droplets areproduced by changing the volume of each pressure generating chamberwhile causing the corresponding piezoelectric vibration element to beflexibly displaced, is designed to displace a wide area of the pressuregenerating chamber. Therefore, the ink droplets can be produced stably.

In order to improve the printing speed of such a recording head,attempts have been made to arrange a great number of nozzle openings perrecording head. Since a head having a great number of nozzle openingshas an extremely low yield, it is also designed to use a plurality ofactuator units A, B, C and fix such actuator units in zigzag to a flowpath unit D having nozzle openings and common ink chambers formedtherein as shown in FIG. 11.

However, for a color printing recording head that requires at leastthree rows of nozzle openings, not only the width of the recording headis increased, but also ink jetting timing control becomes complicatedsince the positions of the nozzle openings that are driven to print anidentical row of data are shifted in a carriage moving directionmutually.

SUMMARY OF THE INVENTION

The invention has been made in view of the aforementioned problems. Anobject of the invention is therefore to provide an actuator unit for alaminated ink jet recording head that can be arranged straight in apaper feeding direction in pluralities.

A second object of the invention is to provide a laminated ink jetrecording head using the aforementioned actuator unit.

A third object of the invention is to provide a method of fabricatingthe actuator unit.

According to the present invention, there is provided an actuator unitfor a laminated ink jet recording head, a plurality of actuator unitsbeing brought into contact with each other at ends thereof and laminatedon a flow path unit including nozzle openings, comprising: a first covermember having piezoelectric vibrators on the surface thereof; a spacerfor forming pressure generating chambers, one surface thereof beingsealed by the first cover member; and a second cover member laminated onthe spacer and having ink jetting outlets communicating with one end ofthe pressure generating chambers and ink flowing inlets communicatingwith the other end of the pressure generating chambers; wherein a pitchat which the pressure generating chambers are arranged is set equal toor less than a pitch at which the nozzle openings are arranged and thewidth of partition walls on an outermost ends of the pressure generatingchambers located at the outermost ends of the actuator is set equal toor more than a width of a partition wall defining adjacent pressuregenerating chambers and equal to or less than 1/2 the nozzle openingarrangement pitch.

The distance between two pressure generating chambers that interpose thecontact line of the two actuator units merely increases by a valuesubstantially equal to the width of the partition wall that defines thepressure generating chambers. Therefore, the nozzle openings that are tocommunicate with these pressure generating chambers come to be arrangedat least at positions corresponding to the pressure generating chambers.Hence, by slightly staggering the nozzle communication holes of the flowpath unit that connect the pressure generating chambers to thecorresponding nozzle openings, the two actuator units can be connectedunder such flow path conditions as to allow ink droplets to be jetted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view showing an embodiment of the invention;

FIGS. 2(a) and 2(b) are sectional views showing the embodiment of theinvention in the form of a structure in the vicinity of pressuregenerating chambers of a single actuator unit;

FIG. 3 is a diagram showing an exemplary method of fabricating a spacerconstituting the actuator unit;

FIG. 4 is a diagram showing another exemplary method of fabricating aspacer constituting the actuator unit;

FIG. 5 is a top view showing an exemplary actuator unit fabricated bythe aforementioned method;

FIG. 6 is a top view showing an embodiment of the invention when arecording head is formed using two actuator units;

FIGS. 7(a) and 7(b) are sectional views showing how nozzle openings andpressure generating chambers are connected around where the actuatorunits are connected to each other;

FIG. 8 is a sectional view showing a laminated ink jet recording head,which is an embodiment of the invention, the recording head being formedusing three actuator units of the invention;

FIG. 9 is a sectional view showing pressure generating chambers andrelated portions thereof in one actuator unit in another embodiment ofthe ink jet print head of the invention;

FIG. 10 is a sectional view showing pressure generating chambers andrelated portions thereof in one actuator unit in still anotherembodiment of the ink jet print head of the invention; and

FIG. 11 is a diagram showing an example of a laminated ink jet recordinghead.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Details of the invention will now be described with reference to theembodiments shown in the drawings.

FIGS. 1 and 2 show an embodiment of the invention. In FIGS. 1 and 2,reference numeral 1 denotes a first cover plate, which comprises a thinzirconia plate having a thickness of about 9 μm and has drive electrodes3, 3' formed on a surface thereof in such a manner that the driveelectrodes 3, 3' confront pressure generating chambers 2, 2' that willbe described later. Piezoelectric vibrators 4, 4' made of PZT or thelike are deposited on the drive electrodes 3. 3'.

Reference numeral 5 denotes a spacer that defines the pressuregenerating chambers 2, 2'. The spacer 5 has through holes that willserve as the pressure generating chambers 2, 2' in such a manner thatthe through holes are arranged at a pitch equal to or less than a pitchP2. The pitch P2 is a pitch at which nozzle openings 30, 30' of a flowpath unit 20, which will be described later, are arranged. The spacer 5is also designed so that a width W3 of a partition wall 5c that definesone pressure generating chamber 2 from another pressure generatingchamber 2' will become about 1/3 the width of each of the pressuregenerating chambers 2. 2'.

Reference numeral 6 denotes a second cover body. On sides of the secondcover body 6 toward which the pressure generating chambers 2, 2'confront each other are ink jetting outlets 7, 7' and on the sidesthereof opposite to such sides are ink flowing inlets 8, 8'. The inkjetting outlets 7, 7' and the ink flowing inlets 8, 8' are formed so asto communicate with the pressure generating chambers 2, 2'.

By the way, partition walls 5a, 5b positioned on both outermost ends ofthe spacer 5 as well as partition walls 6a, 6b on both outermost ends ofthe second cover body 6 are adequately rigid even if width W1, W2thereof are set to a value substantially equal to the width W3 of thepartition wall 5c of the spacer 5 and of a partition wall 6c of thesecond cover body 6 that are formed inside. Therefore, the widths W1, W2are set to values substantially equal to or more than the width W3 ofthe partition wall 5c of the pressure generating chamber 2 andsubstantially equal to or less than 1/2 a pitch P1 at which the pressuregenerating chambers 2 are arranged. Hereupon, the width W1 may be equalto the width W2 or W1 is less or more than the W2.

These members 1, 5, 6 are assembled to an actuator unit 10 by molding aclay-like ceramic material into predetermined shapes and laminating andsintering the molded shapes without using an adhesive.

The actuator unit 10 has a positioning through holes 11 and apositioning through recess in the middle in order to facilitate theassembling operation.

When the spacer 5 that needs such thin partition walls 5a, 5b, 5c is tobe formed of a green sheet 12 made of ceramic material, a groove 13 thatextends as far as cutting lines C, C is formed along a boundary regionso as to match the forming of the through holes serving as the pressuregenerating chambers 2 as shown in FIG. 3.

Upon completion of sintering after drying the green sheet 12, the bothend portions of the sintered sheet 12 are cut away along the cuttinglines C which traverse both ends of the groove 13, so that the widthsW1, W2 of the partition walls 5a, 5b of the pressure generating chambers2, 2' positioned toward both outermost ends can be formed with the sameaccuracy as that of the width W3 of the partition wall 5c that definesthe pressure generating chambers 2.

It may be noted that by forming a projection 15 so as to coincide withthe positioning through recess 14 on the other end as shown in FIG. 4 sothat an actuator unit having the through recess 14 and the projection 15can be prepared as shown in FIG. 5. The thus constructed actuator unitis advantageous in allowing two actuator units to be positioned relativeto each other with ease when each actuator unit is to be set in a flowpath unit.

As shown in FIGS. 6, 7(a) and 7(b), the flow path unit 20 is fixed tothe thus constructed two actuator units 10, 10' by bringing outermostside walls 5b, 5b into contact with corresponding outermost side walls5a, 5a and reinforcing the flow path unit 20 and two actuator units 10,10' with fixing members 17, 17 so as to allow the fixing members 17, 17to mount over a contact line 18. As a result, a recording head havingthe two actuator units 10, 10' arranged on a straight line in tandem canbe completed.

In this case, as shown in FIGS. 7(a) and (b), the partition walls 5b, 5aof the respective actuator units 10, 10' confront one another atportions where the two adjacent pressure generating chambers 2a, 2b thatare in contact with the contact line 18 are partitioned, the contactline 18 being a line with which the two actuator units 10, 10' come intocontact. Therefore, the partition walls 5b, 5a are about twice as thickas each partition wall 5c that partitions other pressure generatingchambers 2.

However, by slightly shifting nozzle communication holes 28, 29 of theflow path unit 20 toward the nozzle openings 30, these pressuregenerating chambers 2, 2, 2a, 2b can be made to communicate with thenozzle openings 30, 30' that are arranged at the predetermined pitch P2.

The flow path unit 20 to which these actuator units 10, 10' are fixed isformed by laminating an ink supply inlet forming substrate 21, a commonink chamber forming substrate 22, and a nozzle plate 23 with adhesivelayers 24, 25 such as thermally fusible films.

Ink supply inlets 27, 27' that not only connect common ink chambers 26,26' to the pressure generating chambers 2, 2' but also serve asconstrictions that utilize pressure effectively, are formed in the inksupply inlet forming substrate 21. The nozzle communication holes 28,28' that introduce ink from the pressure generating chambers 2, 2' intothe nozzle openings 30, 30' are also formed in the ink supply inletforming substrate 21.

Further, the common ink chamber forming substrate 22 is prepared byforming the common ink chambers 26, 26' and nozzle communication holes29, 29'. The common ink chambers 26, 26' receive the ink from a notshown ink tank and distribute the received ink to the respectivepressure generating chambers 2, 2'. The nozzle communication holes 29,29' connect the pressure generating chambers 2, 2' to the nozzleopenings 30, 30.

The nozzle plate 23 is prepared by forming the nozzle openings 30, 30'so as to be arranged on a single line at the predetermined pitch P2.

As described above, the distance between the two pressure generatingchambers 2a, 2b located at the boundary at which the two actuator units10, 10' are connected to each other is substantially twice the width ofthe partition wall 5c that defines the respective pressure generatingchambers 2, 2 since the partition wall 5a abuts on the partition wall5b. That is, a distance P3 between the pressure generating chambers 2a,2b is larger than the distance P1 between other pressure generatingchambers 2, 2.

However, by forming the nozzle communication holes 28, 28' of the inksupply inlet forming substrate 21 and the nozzle communication holes 29,29' of the common ink chamber forming substrate 22 so as to shiftslightly toward the contact line 18, these pressure generating chambers2a, 2b can be connected to each other without causing ink droplets to bejetted out into the nozzle openings 30, 30 at all times, i.e., withoutletting the ink stagnate in the nozzle openings 30, 30.

Specifically, if the pressure generating chambers 2, 2' are arranged ata pitch P1 of about 4/360 inches, then the width W3 of the partitionwall 5c defining the pressure generating chambers 2 can be set to about1/360 inches and this allows the distance P3 between the two pressuregenerating chambers 2a, 2b interposing the contact line 18 therebetweento be set to about 6/360 inches. That is, the distance P3 becomes widermerely by about 2/360 inches than the pitch P1 of the pressuregenerating chambers 2, 2' other than the outermost pressure generatingchambers.

If the nozzle communication holes 28, 28' of the ink supply inletforming substrate 21 and the nozzle communication holes 29, 29' of thecommon ink chamber forming substrate 22 of the flow path unit 20 arearranged so as to position toward the contact line 18, the ink can bedriven out of the nozzle openings 30 smoothly without stagnation in thepressure generating chambers 2, 2' since steps between the upper andlower communication holes 28, 29, 28', 29' are reduced.

As a result, a plurality of actuator units 10 can be arranged in tandemon a straight line with respect to the nozzle openings 30, 30 pitched ata predetermined interval so as to communicate with the nozzle openings30, 30.

While the case where the recording head is constructed by connecting twoactuator units in tandem has been described in the aforementionedembodiment, a recording head may be constructed by connecting three ormore actuator units 10, 10', 10" to the flow path unit 20 having nozzleopenings at the predetermined pitch P2 by making the pitch P1 at whichthe pressure generating chambers are arranged slightly smaller than thepitch P2 at which the nozzle openings 30 formed in the flow path unit 20are arranged as shown in FIG. 8.

That is, assuming that the nozzle arrangement pitch is P2, that thedistance between the ends of the adjacent actuator units is P3, and thatthe number of pressure generating chambers in a single row of a singleactuator unit is N, then the pressure generating chamber arrangementpitch P1 may be set as follows.

    P1=P2-(P3-P2)/(N-1)

The pressure generating chambers in the middle of the actuator units 10,10', 10", e.g., pressure generating chambers 41, 42 of the actuator unit10' in the middle are positioned on vertical lines of nozzle openings51, 52 to which such pressure generating chambers 41, 42 are to beconnected, whereas the pressure generating chambers 44, 45, 46positioned on a right side of the pressure generating chambers 42 inFIG. 8 are gradually deviated from the centerlines of nozzle openings54, 55, 56 to which the pressure generating chambers 44, 45, 46 are tobe connected.

However, if the nozzle opening arrangement pitch P2 is set to 4/360 inchas described above and the number of nozzle openings in a row to whichthe actuator units 10, 10', 10" are connected is set to 32, then adisplacement between the nozzle opening arrangement pitch P2 and thepitch P1 at which the pressure generating chamber 2, 2' are arranged isabout 4.6 μm. Therefore, if the pitch P4 at which the nozzlecommunication holes 28, 28, 28 . . . of the ink supply inlet formingsubstrate 21 and a pitch P5 at which the nozzle communication holes 29,29, 29 . . . of the common ink chamber forming substrate 22 are given as

    P4=P2-2(P3-P2)/3(N-1)

    P5=P2-(P3-P2)/3(N-1),

then, ink is allowed to flow smoothly from the pressure generatingchambers 2 to the corresponding nozzle openings 30.

By making the pressure generating chamber arrangement pitch P1 slightlysmaller than the nozzle opening arrangement pitch P2, the pressuregenerating chambers located in the middles of the actuator units 10,10', 10" are caused to communicate with the nozzle openingssubstantially straight. Further, if the communication holes of the flowpath unit 20 are gradually shifted slightly toward a side end, anincrease in the thickness due to the two partition walls 5a', 5b" of thetwo pressure generating chambers 46, 47 and due to the two partitionwalls 5a and 5b' of the pressure generating chambers 50, 57 can beabsorbed merely by shifting the positions of the communication holes ofthe flow path units confronting the actuator units within the ranges ofthe regions in which the respective actuator units confront. Therefore,four or more actuator units can be connected in tandem.

While the case where a plurality of actuator units are connected in arow has been described in the aforementioned embodiment, it is apparentthat an ink jet recording head for a multi-nozzle color printer can beconstructed simply by arranging a number of actuator units in tandem ina carriage moving direction.

In the aforementioned actuator unit, the pressure generating portioncomprises the first cover plate 1, the piezoelectric vibrators 4 and thedrive electrodes 3 as shown in FIGS. 1 and 2. Alternatively, thepressure generating portion which comprises piezoelectric vibratingplates 100, lower electrodes 101 and upper electrodes 102 so as to seala surface of the space may be applied as shown in FIG. 9. Furthermore,the pressure generating portion comprising cover plates 106,electrically conductive layer 103, heating elements 104 and protectivelayer 105 may be used as shown in FIG. 10. Other constitutions whichmake the pressure in the pressure generating chamber change may be usedfor the present invention.

As described in the foregoing, the invention is characterized in that anactuator unit for a laminated ink jet recording head, a plurality ofactuator units being brought into contact with each other at endsthereof and laminated on a flow path unit including nozzle openings,comprising: a first cover member having piezoelectric vibrators on thesurface thereof; a spacer for forming pressure generating chambers, onesurface thereof being sealed by the first cover member; and a secondcover member laminated on the spacer and having ink jetting outletscommunicating with one end of the pressure generating chambers and inkflowing inlets communicating with the other end of the pressuregenerating chambers; wherein a pitch at which the pressure generatingchambers are arranged is set equal to or less than a pitch at which thenozzle openings are arranged and the width of partition walls on anoutermost ends of the pressure generating chambers located at theoutermost ends of the actuator is set equal to or more than a width of apartition wall defining adjacent pressure generating chambers and equalto or less than 1/2 the nozzle opening arrangement pitch. That is, therecording head provided with the actuator unit has a great number ofnozzle openings on a single straight line and such recording head can befabricated with a high yield. In addition, the width of a color printingrecording head can be reduced.

What is claimed is:
 1. An ink jet recording head comprising:at least twoactuator units each including a plurality of pressure generatingchambers arranged in rows and means for pressurizing respectively saidplurality of pressure generating chambers; and a flow path unitincluding nozzle openings communicating, respectively, with saidpressure generating chambers, wherein said at least two actuator unitscontact each other at ends thereof and extend in a straight line in adirection in which said pressure generating chambers are arranged inrows, the pressure generating chambers in said at least two actuatorunits lying in a single plane, and a pitch at which said pressuregenerating chambers are arranged is set equal to or less than a pitch atwhich said nozzle openings are arranged, and the width of partitionwalls at the ends of said actuator units is set equal to or more thanthe width of the partition walls separating adjacent pressure generatingchambers in each of the actuator units and equal to or less than 1/2 thepitch at which said nozzle openings are arranged.
 2. The ink jetrecording head according to claim 1, wherein P1 represents the pitch atwhich said pressure generating chambers are arranged, and P1 isexpressed as follows:

    P1=P2-(P3-P2)/(N-1);

wherein P2 is the pitch at which said nozzle openings are arranged, P3is a pitch between a pressure generating chamber at the end of oneactuator unit and another, adjacent pressure generating chamber at theend of another actuator unit that is contacted with said one actuatorunit, and N is a number of pressure generating chambers in one row inone actuator unit.
 3. The ink jet recording head according to claim 1,wherein the pitch at which said pressure generating chambers arearranged is substantially equal to 4/360 inches and the width of thepartition walls separating adjacent pressure generating chambers in eachactuator unit is substantially equal to 1/360 inches.
 4. The ink letrecording head according to claim 1, wherein at least one of saidactuator units comprises a positioning through recess on one end of saidat least one of said actuator units in the direction in which saidpressure generating chambers are arranged in rows.
 5. The ink jetrecording head according to claim 1, wherein at least one of saidactuator units comprises a positioning through recess on one end of saidat least one of said actuator units in the direction in which saidpressure generating chambers are arranged in rows, and a projection onan opposite end of said at least one of said actuator units, saidprojection being shaped to fit in said positioning through recess. 6.The ink jet recording head according to claim 1, further comprising:afirst cover member and piezoelectric vibrators formed on a surface ofsaid first cover member; a spacer that defines said pressure generatingchambers and said partition walls, said spacer having one surface thatis sealed by said first cover member; and a second cover memberlaminated on another surface of said spacer and having ink jettingoutlets communicating with one end of said pressure generating chambersand ink flowing inlets communicating with another end of said pressuregenerating chambers.
 7. The ink jet recording head according to claim 6,wherein said flow path unit comprises:an ink supply inlet formingsubstrate for forming ink supply inlets communicating with said inkflowing inlets and first nozzle communication holes communicating withsaid ink jetting outlets; a common ink chamber forming substrate forforming a common ink chamber and second nozzle communication holescommunicating with said first nozzle communication holes; and a nozzleplate for forming said nozzle openings.
 8. The ink jet recording headaccording to claim 7, wherein P1 represents the pitch at which saidpressure generating chambers are arranged, and P1 is expressed asfollows:

    P1=P2-(P3-P2)/(N-1);

and a pitch P4 at which said first nozzle communication holes arearranged and a pitch P5 at which said second nozzle communication holesare arranged are expressed as follows:

    P4=P2-2(P3-P2)/3(N-1),

    P5=P2-(P3-P2)/3(N-1);

wherein P2 is the pitch at which said nozzle openings are arranged, P3is a pitch between a pressure generating chamber at the end of oneactuator unit and another, adjacent pressure generating chamber at theend of another actuator unit that is contacted with said one actuatorunit, and N is a number of pressure generating chambers in one row inone actuator unit.
 9. The ink jet recording head according to claim 7,further comprising at least one fixing member mounted on adjacent onesof said actuator units.
 10. An ink jet recording head as recited inclaim 1, wherein said flow path unit comprises a common ink chamber thatextends continuously from one actuator unit to an adjacent actuatorunit.